Invertebrates
Sponges & Cnidarians
Sponges

Kingdom: Animalia
– Sub Phylym: Porifera (sponges)



Simplest invertebrates
Asymmetrical (no symmetry!)
No tissues, gut or nerves
How Do Sponges Eat?


Filter feeders: feed on tiny plants and
animals
Water carries food into the sponge through
pores (ostia)
– Ostia: holes on the outside of the body

Inside the sponge, collar cells remove food
from the water
– Collar cells: special cells that line the central
cavity of the sponge; they digest food

The water exits through an osculum
– Osculum: hole at the top of the sponge
Sponge Anatomy
• Where does the water enter?
• Where does the water exit?
• What structure on the collar
cells pushes the water up?
Body Part Abilities



If a part of a sponge is broken off, the
missing part can regenerate, or grow back
If a sponge is broken into pieces, new
sponges could form from each piece
If you force a sponge body through a
strainer, the separated cells could come
back together and reform the same sponge!
Kinds of Sponges




All are in the water (most in salt water)
Come in different shapes/sizes
Most sponges have a skeleton made of hard
fibers called spicules
Grouped by their type of skeleton
–
–
–
–
Barrel sponge
Tube Sponge
Finger Sponge
Vase Sponge
Cnidarians


Pronounced “nigh-dare-e-ins”
Kingdom: Animalia
– Sub Phylum: Cnidaria


Invertebrates that have stinging cells
More complex than sponges
– Have complex tissues, a gut & simple
nerves

Include: jellyfish, hydrozoa, sea
anemones and coral
Two Body Forms

Cnidarians have ONE of the two body
forms:
– Medusa: swim through the water
– Polyp: attach to a surface

Some change forms at different times
in their life
Special Cells

All cnidarians have tentacles covered with
stinging cells
– Nematocysts: stinging cells that release spears
into an organism when it brushes the tentacles


Some can release poison
Used for protection and to catch food
Kinds of Cnidarians
**We split them into four classes:
Kingdom: Animalia
Sub Phylum: Cnidaria
Class: Hydrozoa
Scyphozoa
Anthozoa
Cubozoa
Hydrozoans




Hydra, Portuguese Man-o’War
Hydra are always polyps (attached)
Live in fresh and salt water
Many live in colonies
Scyphozoans



Jellyfish
Catch other inverts and fish in tentacles
Spend most of their life as a medusa
Anthozoans




Sea Anemones and Corals
Spend their lives as polyps
Often brightly colored
Live in colonies
Cubozoans
Are square shaped when viewed from
above
 Resemble true jellyfish
 Have well developed eyes
 Are one of the most deadliest animals
in the ocean
